A widely recognized obstacle in treating drug dependence is apparent lack of client motivation for change. Yet there is no current consensus regarding how best to measure and modify such motivation. This project aims to clarify the construct structure of motivation for change in drug abuse/dependence, and simultaneously to test the efficacy of a promising therapeutic procedure for enhancing motivation. The project also represents a novel merger of clinical research and basic science regarding the psycholinguistics of commitment, focusing on verbal interactions of clients and therapists. A series of four studies is proposed with clients presenting for outpatient or inpatient treatment for drug problems. The first three are randomized trials of motivational enhancement therapy (MET), a procedure shown in a series of prior trials to be effective in reducing alcohol use and problems when administered prior to or in lieu of treatment. The target populations for these three trials are female outpatients, male Outpatients and inpatients entering drug abuse treatment programs at UNM-CASAA or the Albuquerque V.A. Medical Center. Subjects will be randomized to receive or not receive a MET intervention prior to entering treatment. A fourth study will examine the impact of a potentially cost-effective group form of MET. Through the use of an extensive common pretreatment assessment battery, these samples can also be combined to conduct factor and cluster analyses of motivational constructs. Psycholinguistic analyses will be conducted with natural language usage of subjects regarding their drug use and desire for change, following on interesting prior findings regarding the language of commitment. Follow-ups will be conducted at 3 months (when maximal impact is expected) and at 6 and 12 months (to determine the maintenance of prior changes and the longer-term impact of interventions). A series of secondary multivariate analyses will be conducted to determine which (among seven) motivational domains optimally predict client behavior change (e.g., treatment compliance, drug use outcomes), and to determine "matching' characteristics that mark differential responsiveness to MET. Beyond a clear evaluation of the efficacy of MET, the study will contribute new knowledge regarding the structure, impact, and measurement of client pretreatment motivational characteristics, and may yield measurement and intervention tools of practical importance in the treatment of drug problems.